Rectifying apparatus for producing constant voltage



I A rosmo KURIMURA 3,270,272

RECTIFYING APPARATUS FOR PRO DUCING CONSTA NT VOLTAGE Filed June 7, 1962 e Sheets-Sheet 1' 3,270,272 4 nsq'mruue nmmus FOR mouu'cmc cons-um vovrms Filed June 7. 1962 Aug. 30 1966 TOSHIO KURIMURA 6 Sheets-Sheet 2 Fig....3/1,,

' -"I- 30(1966 J 'rosmo KURIMURA 3,270,272

RECTIIYING APPARATUS FOR PRODUCING CONSTANT VOLTAGE lilod Juno '1. 1962 6 Shuts-Sheet 3 3,270,272 RECTIFYING APPARATUS FOR PRODUCING CONSTANT VOLTAGE Toshio Kurimura, Setagayn-ku, Tokyo, Japan, assignor to Koknsai Dcnshin Denwa Kabushiki Knhha, Chiyodaku, Tokyo, Japan, a joint-stock company of Japan Filed June-7, 1962, Ser. No. 200,880

Claims priority, application Japan, .lune24, 1961, 36/21,980

6 Claims. (Cl. 321-42) This invention relates to rectifying apparatuses for producing constant voltage. More particularly, the present invention relates to a new rectifying apparatus employing 3 rectifie'rs with control electrodes the conductive periods of which are, in successive order,'shifted directly and automaticall y in response to variations'in the voltage of alterhating current power source.

- .ln general, the direct-current output voltage of a rectifying apparatus varies in accordance with the alternating current input voltage. Accordingly, in order to maintain the rectified outputvoltage at a very stable value, it

has been common practice to stabilize the voltage of the input alternating current or, to stabilize the converted voltage of direct current by utilizing such a circuit as a vacuum tube type stabilizer which is controlled by the converted output voltage component. However, the appa'ratus of such prior art proposed heretofore have had numerous disadvantages, for example, slow response, com:

plicated and high cost construction, high power loss, and

incapabilityof being applied to apparatus of high capacity.

'lt'isjan object of the present invention to solve the difficulties as stated above and to provide a new rectifying apparatus which is capable of producing an extremely stable, converted output voltage which is-almost completely unaffected by variations in the voltage of the alterhating-current power source.

It is another object of the invention to provide a rectitying apparatus'for producing a constant voltage as stated above which, moreover, has a relatively simple construction and a. simple and reliable operation. It is still another object to provide a rectifying apparatus asstated above which has a wide range of applicability. I g

'lt is'a further object to provide a rectifying apparatus as stated above which can be made in a compact or simple form. Still further objects and advantages will presently become apparent from-the description-presented hereinafter.

The foregoing objects have been achieved by a rectifysing apparatus, according to the present invention, for

producing from an alternating-current supply a substantially constant direct-current voltage by utilizing grid controlled rectifiers or the like connected to the load through at least one choke coil, wherein said controlled rectifiers are, successively, rendered conductive at every instant when a respective voltage, which is proportional to and delayed by11r/2 in phase against a respective ditference voltage between every two alternating voltages between which the rectified current is commutated, coincides with a direct-current reference voltage.

The above-described rectifying apparatus for producing a constant voltage which is provided by the present invention is one wherein the direct-current output voltage is maintained substantially constant, even when variations exist in the voltage of the power source, and stable operation. in a simple, yet positive manner is obtained.

The rectifying apparatus for producing constant voltage according tothis invention is not of the so-callcd feed- ,back type which has been principally used heretofore, and

of the rectifying apparatus according to the invention to,

Patented Auguat 30, 1966 2' output voltage and utilizing tion is accomplished so that variations of the alteratingcurrent voltage are directly without employing a feedback loop and automaticallycorrected, wherefore the apparatus is of a type which may well be called a direct control type." Accordingly, this apparatus has highly desirable characteristics,extremely high sensitivity, and,

moreover, almost no offset. I

The nature and details of this invention, as well as the manner'in which its objects and numerous advantages may best be achieved, will be more clearly apparent by reference to the following detailed description of a few; representative embodiments of the invention, taken in conjunction with the accompanying drawings in'which the same and equivalent parts are designated by the same reference numerals and letters, and in which: FIG. 1 is an electrical diagram, showing an embodiment of the invention in an application-to half-wave rectification of :1V three-phase, alternating current, inwhich a power transformer of star connection type is used;

FIGS. 2A, 2B, and 2C are waveform diagramsof describing the operation of the embodiment shown in FIG. l;

FIGS. 3A, 3B, and 3C are vector diagrams indicating the phase relationships of control voltages to be used for rectifying a three-phase, alternating current;

FIG 4 is an electrical connection diagram showing another embodiment of the invention in an application to the rectification of two-phase alternating current (this j term being-used herein to distinguish it from the full-wave rectification of single-phase, alternating current);

FIGS. 5A, 5B, 5C, and 51) are graphical representations showing waveforms for describing the operation of the embodiment shown in FIG. 4;

FIGS. 6A, 6B, and so are block diagrams for describing the manner of production tifiers with control electrodes;

FIG. 7 is an electrical connection diagram showing an embodiment of the invention in the case of its application to full-wave rectification of single-phase, alternating current; I t

FIG. 8 is an electrical connection diagram showing an embodiment of the invention in the case of its application torectification of six-phase, alternating current; and

'FIG. 9 is an electrical connection diagram showing an of control voltages of recembodiment of the invention inan application to full-* wave rectification of three-phase alternating current.

' Referring to FIG. 1 which is a case of "an, application half-wave rectification of a three phase alternating current, and which will first be described. A three-phase 'transfonner 1 with its secondary windings connected in a star configuration supplies alternating currents to rectifiershwith controlelectrodes 2, 3, and 4, the outputs of which are commonly supplied, through a choke coil -5, to

, a load 6. .A smoothing capacitor 7 is connected in parallel' with the. load t On the other hand, in order to generate the control voltage of each of the rectifiers with the control electrodes 2,3, and 4 resistances 8, 9, and 10 for limiting currentsare connected to the output terminals of the three phases of the transformer, and the other ends of these resistances are connected, by way of rectifying elements ll, 12, and 13, respectively, to a reference-voltage source 14. The voltages at the respective junctions between these resistances 8, 9, and 10 andthese rectifying elements 11, 12, and 13 are applied by way of differentiating capacitors l5, l6, and 17,' respectively, to the control electrodes of which. accomplishes control of rectifiers withcontrol clec- I trodes by detecting the variations in the direct-current the corresponding rectificrs with control electrodes 4, 2.

and 3. Resistances 18, 19, and 20 which are connected to these electrodes form,

respective differentiation circuits.

this detected voltage. in therectifying apparatus according to this invention, rectificaq of the first phase,

the period from t, to 1;, the voltage e voltage source 14 is indicated in relation to Referring to FIGS. 2A, 2B, and 20, the case wherein 'fiers with control electrodes 2,

' become equal to the input voltage o of the choke coil That is, in the period from t control electrode 4 is conductive,

is substantially equal to the voltage e, of the third phase.

A power source 21 which is connected to the other ends of the resistances 18, 19 and 20 applies optimum bias voltage to the rectifiers with control electrodes and, normally,

maintains these rectifiers in their cut-off states.

f The operation of the above-described rectifying apparatus is described below with refernce to FIGS. 2A. 2B,"'and 2C. In FIG. 2A, the heavysolid lines represent the input voltage 0 the heavy lines, in this rectifying apparatus, the'voltage the voltage eg of the second phase, and the voltage e of the third phase are so controlled that they are rendered conductive by starting the recti- 3, and 4, in sequence, to

to 1 the rectifier with whereby the voltage s In the same manner, in the period from t, to 1,, the voltage e is substantially equal to-the voltage e and in is substantially equal to the voltage 0 p In order to successively render the rectifiers with control ele ctrodesconductive an impulse having a waveform as indicated by the heavy linev in FIG. 2B is generated at the junctions between the respective resistances 8, 9- and I0 and rectifying elements 11, 12 and 13, t connection which comprises resistances rectifying elements 11,12 and 13, and the reference volt- :a'ge source 14.

'- venience in description,

,the' voltage c of the second phase by the use of the rejsistance 9, the rectifying element 12, and theretereneein the regulation 8, 9 and 10, the

' In FIG. 213, however, especially for cononly the waveform obtained from FIG. 2A.

-the rectifier with control electrode 2 is conductive will 1 now be considered. The symbol e, designates the voltage *produced 'at'the junction between thev resistance '9 and '..t he rectifying element 12. since the second-phasevoltage e; exceeds thevoltage 'E,

of the reference power source 12, becomes conductive, whereby the state 'e.=E, is maintained. This voltage age e is zero;

In the interval from-t to 1 14, the rectifying element e,, is differentiated by the difyferentiation circuit composed of the condenserl6 and the resistor 18. Accordingly, .hea'vy'line in FIG. 2C is obtained at the control electrode terminal of the rectifier, with control electrode 2. Since the voltage e, is constant in the interval r, tol the voltbut at the time it rises abruptly to a value corresponding to-the differentiated value of the volta voltage e as indicated by the age e. This abrupt rise of the voltage e at r, is utilized t, to fire input voltage a or start the rectifier with contrrol electrode 2. At the time i; when the rectifier 2 is conductive, the

', rectifier with control electrode 4'is, as indicated in FIG.

2A, lowerthan the input voltage e of the 'choke'coil 5 {,(this voltage e corresponding to the voltage applied on l voltage e,

rectifiers with control electrodes 3 and 4, As described in the foregoing disclosure, of the conductive states of the three rectifiers with control electrodes 2,3 and 4 is accomplished with phase difier- 1 ence of t \gthe'cathode of the rectifier with-control electrode 4).

Consequently, the rectifier with control electrode 4 is I cut off.

As described above, a control signal obtained from the is used for igniting the rectifier with control electrode 2, while, in the same manner, control signals obrained from voltages e, and e, are usedfor igniting the respectively. the switching whichis the same as the phase differencev between the phases of theinput alternating current.

v If the rectifiers with .the'ti'apsfonner 1 are connected in the reverse polarities control electrodes 2, 3 and 4 and of the choke coil 5. As indicated by to those of the case illustrated in FIG. 1, and mo reover,

the reference voltage source 14 is connected in the reverse polarity to the illustrated,the output voltage E will be obtained, at the output side of the choke coil 5, at a lower potential than the common return terminal which is sometimes used as'the ground terminal. While, in the description presented hereinafter, only the case wherein a voltage of positive polarity is obtainedrwillbe illustrated, it will be apparent'that it is possiblettoobtain a voltage of'negative polarityby making necessary changes therein.

The reason why the output'voltage-E is stably maintained at a constant value by the abovedescribed operation, without being influenced by 'variat'ions'in the input alternating-current voltage, will now be analyzed in connection with'FIG. 2A. If the capacitance of the smoothing capacitor 7 of the output side is assumedto be sutficiently large, and the'ripple component and the, resistance com- 5 are, assumed to be negligible,

ponentof the choke coil H the outpu oltage E in FIG. 2A,, will assume a value corresponding to the meanvalue of the'inputvoltage e of the choke coil 5. That is, the output voltage E will assume such a value that,

the curve c and the line E included in the portion whereapplied to the anode terminal of the' y From Equations 3, 4, and l," thefollowing tained.

where: semi wn; and I v T is therperiod of the alternating-current"voltage;' t On the other hand, when the lefthand side of EquavThe righthand side of the above equationeorresponds to an area produced by integrating the voltage difierence between adjacent phasest line voltage) in thet period from the time when the dilierence is zero (for example: l to the time when switching of conductive states oithe rectifierswith control electrodes takes place (for example:

t,). In the case of switching from e to e, in .FIG. 2A, if the time when e, and e, intersectv is denoted by i the portion corresponding to (A i-A may bei represented by the following equation. 1' 1w a,

Since the input is'a three-phase alternating current, the variable (q e also assurnes a sinusoidal wave, and its maximum amplitude is /3E,, where. E, is. the maximum amplitude of e 2 and c may be rewritten as follows:

tion 1 is now considered, his quantity-(A f-Fitg) is obtained by subtracting the area enclosed between the zero line and the line corresponding to Es] from one half of the areaproduced by integrating the line voltage'over its to e; antic; in the half period .(this line voltage relates ease of.FIG. 2A). That is,

voltage e, is in the form of a cosine wavewithits maximum negative value at thetime 15.!herefore, v

wo s a (6) in FIG, 2A, the area between line E included in the por- Accordingly, .Equation 2 21 EQHT I relation is ob- 0n the'other hand, as may be seen from FIG. 2B, the

ages.

ages have been described above. I of polyphase (n-phase) alternating current as, for ex- Accordingly, the following relation is obtained from EquationsSand 6.

' That is, the aforedescribed rectifying apparatus provides an output voltage E, which is expressed by Equation 7. Since this relation is independent of voltage of the alternating-current power source, the rectified output of this rectifying apparatus is constant even when voltage of the alternating-current power source varies, and the apparatus operates as a rectifying apparatus for producing a constantvoltage.

' The rncthod of producing signals for controlling the rectifiers with control electrodes. in the case of rectification of three-phase alternating current as described above may be further described 'with reference to vector diagramsas shown in "FIGS. 3A, 3B, and 3C. In the case of a star connection, the voltages e e and e; have a displacement of 21'r/3-as indicated in FIG. 3A. The symbols Eg E 3, and E designate respectively difference volt- As previously'descrihed, when switching from e;, to 2 is performed, a voltage corresponding to the integrated value of the difference voltage E between the phase voltage a; which is conductive and the phase voltage e; which is successively conductive may be considered to be used inorder to make it refer to the reference voltage. (In the example of FIG. 2, the abovesaid difference voltage is represented by the light line waveform shown in FIG. 2C, and the waveform corresponding to the :integ'rated value of this difference voltage is that shown in FIG. 2B). In the example of difference voltage E since the voltage e, having a phase difference of 1r/2 with vrespect to; E corresponds to the present voltage, the

voltage 2 is adopted as a voltage for generating the control signal-in this case. Even if the amplitude of the present voltage is not equal to that of c if their phases are the same, this voltage may, of course, be used similarly as a control voltage by selecting suitably the value of the reference voltage E in accordance with this voltage. Similarly,whcn commutation from s; to e, is performed,

the-voltages; having a phase difference of 1r/2 with respect to the difference voltage B is used as a voltage for the purpose of generating a signal for switching; and

- when switching from e, to e; is performed, the voltage e having a phase difference of 1/2 with respect to the difference voltage B is used as a voltagefor the purpose of generating a signal for switching as shown in FIG. 1. v

In the case wherein the connection of the transformer is a ring connection, and a voltage having a phase diff ference of 1r/2 with respectto the difference voltage as in the previous case is not directly obtainable from the voltage of the altemating-current power source, voltages such as 0 c and 0 can be generated by the system indicated in FIG. 3B and used as voltages for the purpose of generating signals for switching.

Systems-for generating control signals through the utilization of thephase relationships of the various phase volt- In'general, in the case ample, shown in FIG. 3C, wherein a signal having a phase difference of 1/2 with respect to a line voltage E 1 6 forms indicating the operation of the embodiment of FIG. 4 as described below.

By means of rectifying elements 28 and 29, a voltage e, corresponding to a'difference voltage as indicated by the heavy linein FIG. 5B is produced at a resistance 30, and this voltage e together with the voltage 13 of a reference voltage supply 31, is applied to a trigger cireuit 32. Then, a rectangular pulse wave e having transition instants corresponding to the instants when thevoltage e, coincides with the reference voltage E in the direction in which it becomes. zero, is generated as indicated in FIG. 5C. This voltage e (or its differentiated signal) is passed through a delay circuit 33 having a retardation time of TM and becomes a control voltage e (FIG.

5D) having a phase difference corresponding to 174 of v the voltage of the a-lternating current' power source with respect to the voltage e This control voltage e when a it is regarded froma different viewpoint, may be considered as arectangular wave having transition instants corresponding to the every instant when a voltage e having a phase difference of 1r/2 with respect to the line voltage e (that is, the signal e shown by broken line in FIG. 5B) coincides with the reference voltage 15,. Al-

though this control voltage e is applied common to both of the control electrodes of the rectifiers with control electrodes 23 and 24, only the rectifier with control elec- I trode which has an anode voltage higher than its cathode voltage becomes conductive at their respective. transition instants. v

Accordingly, as the input voltage e of thefcholte coil '25, the voltage indicated by the heavy line in FIG. 5A; is obtained. Since, for the delay circuit 33, a circuit having a delay time corresponding to T/ l can be used, an active circuitsuch as a monostable multivibrator may be used for this circuit.

In the two embodiments described above'in connection with FIGS. 1 and 4, two methods of generating control voltage of the rectifiel's with control electrodes were described. Furthermore, in conjunction with FIGS. 3A, 3B, and SSC, the description has been presented from the viewpoint of phase position. To facilitate a clearer understanding of the system for generating the said control signals, a summary description to be taken in conjunction with FIGS. 6A, 6B, and 6C is presented below.

In the case indicated in FIG. 6A, the line voltage 34 between the phase which isin now a conductive state and the phase which is next to become conductive is,

in a. referencev circuit 35, first referred. to a reference voltage 36, and then the output signal of .this reference circuit 351's phase shifted in a delay circuit 37 having a delay time corresponding to T/4'of the voltage of the alternating-current source, whereby one control signal is obtained at the output terminal 40 of the delay circuit signalsare obtained by establishing reference with the respective reference voltages after effectuation of the necessary phase shift. As in the case of FIG. 6A, it

is possible to derive the input signal of the phase shifte 46 from the output of thephase shifter 44.

The system employed in the case, indicated in FIG.

6C, differing from that in the. case of FIG. 6A or 6B in I which one difference voltage or one phase voltage is utilized, utilizes each of the corresponding difference voltages or phase voltages. The control signal producing circuits 57, 58, 59, are each provided with means for establishing a reference with respect to the reference voltage60 and means for effecting a necessary phase shiftafter correction of the waveform or conversion to 'pulse and the delay .time'of, are integral number v be utilized. d wOrie embodiment of the invention in the case of its application to rectification of 'a six-phase alternating curthree-phase alternating current.

'- same as that of the case shown in FIG. 1 except that the 7 signal in'cusc of necessity. in the case of FIG. 6A, a combination of the reference circuit 35 and the delay circuit 37 corresponds to these control signal producing circuits, Interms of the embodiment of FIG. 4, a combination of the trigger circuit 32 and the delay circuit 33 corresponds to these control signal producing circuits.

Furthermore, while the above description has related exclusively to cases in each of whichthe. original signal for producing a control signal is derived directly from the main power transformer, it is also possibleto derive Ithisoriginal signal by using an auxiliary transformer provided as an attachment to the main power transformer.

windings of the main transformer.

For example, in the case of a single phase, it is possi ble to convert a single-phase to two-phases; or in the case of ring connection, the ring connection can be converted to a star connection.

Finally, in, order to disclose the rectifying apparatus according to the present invention still more, the following embodiments thereof are described.

7 In FIG. 7is illustrated an embodiment'in the case of the application of the invention to full-wave rectification of a single, phase alternating, current. "The control systemof this embodimentdiffers from the case of rectification of a two-phase alternating current described in connection with FIG. 4 in that a neutral point cannot rent is shown in FIG. 8. This embodiment may be understood to be of a device wherein three circuits, each I of which is that of the rectification of two-phase alternab ing current shown in FIG. 4, are provided in parallel arrangement.

t FIG. 9 illustrates another embodiment of the invention in the case of its application to full-wave rectification of This embodiment is the number ofthe rectifiers with control electrodes and the number'of control signal producing circuits (these may be supposed 'to be the same as those previously described,

. or, in this embodiment, it may be considered that a control signal producing circuit 112 .indicates the combination of the resistance 8, rectifying element II, and capacitor of FlG. l) are doubledas compared with the case of FIG. 1. In operationalso. the number of switching of l conductive state is double that in the case illustrated in FIQI. That'is, control signals of the rectifiers belongingj to the first group (110, 111 and 112) are the same as those ofthe rectifiers 2, 3, and 4 in FIG. I. Howi ever, phases of thecontrol signals of the rectifiers belonging to the second group'tllll, 114, and 115) are made to ditfenrespectively, from those of the control signals for said first group in order to accomplish the full-wave rectification of three-phase alternating current. With this difference in mind, the operation of the embodiment .01? FIG. 9 will be easily understood by analogy. with that of the embodiment shown in FIG. I' The'circuit di- :agrain of FIG. 9 is shown without any bias circuit for the sake of simplicity in illustration.

. If, in'each of the above-described embodiments, the .reference voltage is adapted to be variable, it will be possible to set the output voltage E correctly and accurately to a desired voltage within a predetermined range. (Shown in only FIGS. 7, 8, and 9.)

In this type of rectifying apparatus, in general, the ,phase position of the current of any phase lags with req-speet to its phase position of voltage, and the power facgtOr thereof drops. If necessary, however, the power factor ofthe rectifying apparatus can be improved by-connecting a phase-advancing capacitor or a phase-advancing avnchrc'nione machine to the primary sideorthe secondary In this, case, it is possible to adopt the most'simple, reliable, but still stable control circuits without any limitations being imposed by the connection system of the side of the main power transformer. Furthermormsince the above mentioned phase tag has the characteristic of varying in accordance with the variation of the voltage of the alternating-current power source, it is also possible to maintain the powerfactor always at a desirable value by controlling the current of the aforementioned phase advancer by means of the power source voltage. (The case wherein a phase advancer. is applied to the primary side is indicated in only FIGS. '7, -8, and 9.)

. In the aforesaid description, it is assumed that eachof said choke coils is connected toithe reetifierswith con-" trol electrodes and the output voltage or currentv is obtained through'the choke coils. However, as will. be

understood by analogy'with the conventional technique of these rectifying apparatuses, each'of thechoke coils can be connected to either of the output terminals of plusor minus potential except the embodiment of FIG. 8. 'As. described" in the foregoing disclosure, in the -rectifying apparatus for producing a constant voltage according, to the presentinvention, since a control systemuimwhich rectifiers, themselves, are directly and automatically controlled in response to variations in the "voltage of:;,alte rnat ing-current power source is used, no limitations-are imposed on-the capacity of the said rectifying apparatus against the case of. rectifying apparatus of feedgback type for producing constantv voltage in which suehcdmponents' as vacuum uibes are used. Accordingly, the present invention can be readily applied also-to reetifying -.npparatax for power sources of high capacity .Moreover, this advantage atfords compact construction-whereby;.-rectifying apparatus of unconventionally small size can be pro vided.

Furthermore, sincein the rectifyingapparatus,according to the present invention, sensitivity and; reliable eon,-

trol are obtainable, the, present invention is applicable to a wide range of power sourceapparatus,

Although this invention has beendescribed with respect I to a few particular embodiments .thereof, itis not to be. so limited as changes and modificationsmay be made therein which ,arewithin the full intendedscopeof the invention, as defined bythe appendedelaims.

What I claim is: 1. A rectifying apparatus for producing ajsubstnntially constantdirect-current voltage, comprisingan alternating current supply source connected in a three-phasestar con:

figuration and having terminals, three controlled rectifiers respectively connected in the.same, sense to said terminals of said source, ignition means comprising three resistors, three rectifier elements, three capacitors and a terminal of-said alternating current, sourw, whereby in operation said controlled rectifiers are successively l en dered conductive in operation to supply rectified. current to a load, and a choke coil connected to receive s'aid rectified current and connections to apply, the rectified current from said choke coil to said load. d

2. A rectifying apparatus for producing a substantially constant direct-current voltage comprising, an alternating. current supply source having a three two-phase star configuration having terminals, two-phase rectifying circuit means comprising two controlled and two uncontrolled rectifiers each connected to each other at the output side thereof in a full-wave rectification bridge circuit configuration connected to corresponding two-phase terminals of said alternating current source, difierence voltage means comprising two auxiliary rectifiers connected in series backto-back other and connected-ate saidsource to obtain from said two auxiliary rectifiers and said uncontrolled rectifiers a difference voltage between terminals of said source, means to develop in operation a direct-current reference voltage, ignition means for generating ignition signals at every instant when said difference voltage coincides with said direct-current reference voltage and for shifting, by a quarter period of-the alternating-current of said sourcesaid ignition signals, connections for applying said ignition signals in a shifted condition to control said two controlled 'rectfiers, whereby said two controlled rectifiersare alternately rendered conductive to supply the rectified current to a load, and a choke coil connected to receive the rectified current and apply it to said load.

3. A rectifying apparatus for producing from an alterhating-current supply source a substantially constant di- 1 two alternating voltages between which the rectified current is commutated, ignition means for generating ignition signals at every instant when any voltage derived coincides ,with said direct current reference voltage and for applying said signals to said rectifiers, whereby said controlled rectifiers are successively rendered conductive to supply rectified current to a load, at least one choke coil for re- 3 ceiving the rectified current, and connections from said choke coil for connecting aload'thereto for receiving said rectified current therefrom.

4, A rectifying apparatus for producing a substantially constant direct-current voltage, comprising an alternatingcurrent supply source having a center connection and terminals, two controlled rectifiers respectively connected in the same sense to the terminals of said source, difference voltage means connected to said center connection comprising two diode rectifiers connected in series back-toback to each other and connected to said terminals of the source to obtain from said two rectifiers and the source a difierence voltage, a direct-current reference voltage source connected to said center connection and a load, ignition means connected to said reference voltage source and the junction of said diode rectifiers for shifting by a quarter period of the alternating-current of said source said difference voltage and for generating ignition signals at energy instants when said difference voltage in a shifted condition-coincides with said direct-current reference voltage source and applying said ignition signals to control said controlled rectifiers, whereby said controlled rectifiers are alternately rendered conductive to supply the rectified current to a load, a choke'coil connected to receive the rectified current, and connections from said choke coil for connecting the load thereto for receiving saidrectified current therefrom.

5. A rectifying apparatus for producing a substantially constant direct-current voltage, comprising an alternatingcurrent single phase supply source, two controlled and two uncontrolled rectifiers each connected to one another in back-to-back to each other and connected to terminals of said source to obtain from said two auxiliary rectifiers and said uncontrolled rectifiers a difference voltage between terminals of said source, ignition means for shifting by a quarter period of the altemating-current of said source said difference voltage and for generating ignition signals at every instant when the shifted difference voltage coincides with said direct-current reference voltage, connections for applying said ignition signals to control the two controlled rectifiers, whereby said controlled rectifiers are alternately rendered conductive to supply rectified current to a load, a choke coil connected to receive said rectified current for application to said load therethrough. I

6. A rectifying apparatus for producing a substantially constant direct-current voltage from an alternating-current supply source having a three-phase star configuration comprising, two-phase rectifying circuits each comprising two controlled and two uncontrolled rectifiers each connected to one another in a full-wave rectification bridge circuit connected to corresponding two-phase terminals of said source, means to develop in operation a direct-current reference voltage, difference voltage means comprising two auxiliary rectifiers connected in series back-to-back to each other and connected to said source to obtain from said two auxiliary rectifiers and said uncontrolled rectifiers a connected'to receive the rectified current and apply it to.

said load therethrough.

' References by the Examiner UNXTED STATES PATENTS Feltman 321 -18 JOHN F. COUCH, Primary Examinern I Q A. r. GAJARSA, w. E. RAY, Assistant Examiners. LLOYD MCCOLLUM, Examiner. 

1. A RECTIFYING APPARATUS FOR PRODUCING A SUBSTANTIALLY CONSTANT DIRECT-CURRENT VOLTAGE, COMPRISING AN ALTERNATINGCURRENT SUPPLY SOURCE CONNECTED IN A TREE-PHASE STAR FIGURATION AND HAVING TERMINALS, THREE CONTROLLED RECTIFIERS RESPECTIVELY CONNECTED IN THE SAME SENSE TO SAID TERMINALS OF SAID SOURCE, IGNITION MEANS COMPRISING THREE RESISTORS, THREE RECTIFIER ELEMENTS, THREE CAPACITORS AND A REFERENCE DIRECT-CURRENT SOURCE, SAID RESISTORS BEING RESPECTIVELY CONNECTED TO SAID ALTERNATING CURRENT SOURCE AND CONNECTED IN COMMON TO SAID REFERENCE DIRECT-CURRENT SOURCE RESPECTIVELY THROUGH SAID RECTIFIER ELEMENTS, CONNECTIONS CONNECTING SAID REFERENCE DIRECT-CURRENT SOURCE TO A NEUTRAL POINT OF SAID ALTERNATING CURRENT SOURCE, IGNITION SIGNALS FOR EACH CONTROLLED RECTIFIER FROM SAID CAPACITORS AND A CONNECTION JUNCTION BETWEEN A RESISTANCE AND A RECTIFIERING ELEMENT CONNECTED TO RESPECTIVE PHASE TERMINAL OF SAID ALTERNATING CURRENT SOURCE, WHEREBY IN OPERATION SAID CONTROLLED RECTIFIERS ARE SUCCESSIVELY RENDERED CONDUCTIVE IN OPERATION TO SUPPLY RECTIFIED CURRENT TO A LOAD, AND A CHOKE COIL CONNECTED TO RECEIVE SAID RECTIFIED CURRENT AND CONNECTIONS TO SUPPLY THE RECTIFIED CURRENT FROM SAID CHOKE COIL TO SAID LOAD. 